The hydrophobin EAS from the fungus Neurospora crassa forms functional amyloid fibrils called rodlets that facilitate spore formation and dispersal. Self-assembly of EAS into rodlets occurs spontaneously at hydrophobic:hydrophilic interfaces. While hydrophobin rodlets share many structural characteristics with disease-associated amyloid fibrils, they further pack laterally to form amphipathic monolayers. These monolayers adhere tightly to surfaces and reverse their wettability, making them attractive for coating hydrophobic solids such as carbon nanotubes.

An atomic structure of the assembled rodlets would offer insights into the hydrophobin assembly process and opportunities to engineer hydrophobin-based products using rational design strategies. While a number of hydrophobin structures in the solution state have been determined, detailed structural information from the assembled rodlets has proved elusive owing to their inherently insoluble and non-crystalline nature.

We will present the progress made towards building a molecular picture of hydrophobin rodlet monolayers using solid-state Nuclear Magnetic Resonance (ssNMR) spectroscopy. NMR studies on isotopically labeled hydrophobin rodlets revealed a two-fold molecular composition including a substantially disordered region and a structured core, with chemical shifts pointing to the presence of newly formed β-sheet structural elements. Our findings provide direct evidence for conformational change upon monolayer assembly and the presence of a core structure rich in β-sheet, both of which are consistent with the current model of EAS assembly based on peptide inhibition assays and mutagenesis studies.